commit fc75cdfa5b43ac4d3232b490800cd35063adafd3
author Heiko Carstens <heiko.carstens@de.ibm.com> Sun Jun 25 05:49:10 2006 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> Sun Jun 25 10:01:22 2006 -0700
tree 0529ffd9633667457d5340a09b3cb352d09436d2
parent 04a3446c90137a473837288b04b517b19dc67a0d

[PATCH] cpu hotplug: fix CPU_UP_CANCEL handling

If a cpu hotplug callback fails on CPU_UP_PREPARE, all callbacks will be
called with CPU_UP_CANCELED.  A few of these callbacks assume that on
CPU_UP_PREPARE a pointer to task has been stored in a percpu array.  This
assumption is not true if CPU_UP_PREPARE fails and the following calls to
kthread_bind() in CPU_UP_CANCELED will cause an addressing exception
because of passing a NULL pointer.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index f8d540b..f06d059 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4756,6 +4756,8 @@
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
 	case CPU_UP_CANCELED:
+		if (!cpu_rq(cpu)->migration_thread)
+			break;
 		/* Unbind it from offline cpu so it can run.  Fall thru. */
 		kthread_bind(cpu_rq(cpu)->migration_thread,
 			     any_online_cpu(cpu_online_map));

kernel/softirq.c

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 336f92d..9e2f1c6 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -470,6 +470,8 @@
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
 	case CPU_UP_CANCELED:
+		if (!per_cpu(ksoftirqd, hotcpu))
+			break;
 		/* Unbind so it can run.  Fall thru. */
 		kthread_bind(per_cpu(ksoftirqd, hotcpu),
 			     any_online_cpu(cpu_online_map));

kernel/softlockup.c

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index 2c1be11..b5c3b94 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -127,6 +127,8 @@
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
 	case CPU_UP_CANCELED:
+		if (!per_cpu(watchdog_task, hotcpu))
+			break;
 		/* Unbind so it can run.  Fall thru. */
 		kthread_bind(per_cpu(watchdog_task, hotcpu),
 			     any_online_cpu(cpu_online_map));

kernel/workqueue.c

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f869aff..565cf7a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -590,6 +590,8 @@
 
 	case CPU_UP_CANCELED:
 		list_for_each_entry(wq, &workqueues, list) {
+			if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
+				continue;
 			/* Unbind so it can run. */
 			kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
 				     any_online_cpu(cpu_online_map));